/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Hua YY
 * Date: 2024-11-20
 * Time: 16:40
 */
class Solution8 {
    public int[][] matrixBlockSum(int[][] mat, int k) {
        int m = mat.length , n = mat[0].length;

        //1：初始化dp前缀和数组
        int[][] dp = new int[m+1][n+1];
        for(int i = 1 ; i < m+1 ; i++){
            for(int j = 1 ; j < n+1 ; j++){
                dp[i][j] = dp[i-1][j] + dp[i][j-1] -dp[i-1][j-1] + mat[i-1][j-1];
            }
        }

        //2:处理前缀和数组
        int[][] ret = new int[m][n];
        for(int i = 0 ; i < m ; i++){
            for(int j = 0 ; j < n ; j++){
                int x1 = Math.max(0,i-k)+1 , y1 = Math.max(0,j-k)+1;
                int x2 = Math.min(i+k,m-1)+1 , y2 = Math.min(j+k,n-1)+1;
                ret[i][j] = dp[x2][y2] - dp[x2][y1-1] -dp[x1-1][y2] + dp[x1-1][y1-1];
            }
        }
        return ret;




    }
}
public class Test8 {
}
